Radiation image erase unit for use with stimulable phosphor sheet

ABSTRACT

A radiation image erase unit for erasing a residual image from a stimulable phosphor sheet with erasure light is disposed in the vicinity of an image read-out unit which converts light emitted from the stimulable phosphor sheet upon stimulation thereof into an electric signal. The radiation image erase unit comprises a box-shaped casing having a slot for passage of the stimulable phosphor sheet therethrough into the casing, and erasure light sources disposed in the casing for emitting the erasure light. A pair of rollers is mounted on the casing adjacent to the slot for introducing the stimulable phosphor sheet into the casing. The casing has reflective inner surfaces for reflecting the erasure light effectively, and a heat radiator for discharging out heat generated by the erasure light sources as they are energized.

BACKGROUND OF THE INVENTION

The present invention relates to a radiation image erase unit for usewith a stimulable phosphor sheet, and more particularly to a radiationimage erase unit in the system in which a stimulable phosphor sheet witha radiation image stored therein is exposed to stimulating rays, andlight is emitted from the stimulable phosphor sheet in proportion to thestored radiation energy and read out by an optical image read-out devicefor conversion into electric signals representing the radiation image.The radiation image erase unit is arranged such that when the radiationimage which remains on the stimulable phosphor sheet after theirradiation image has been read out is to be erased upon exposure toerasure light, the heat radiation from the erasure light source isforcibly discharged out to protect the stimulable phosphor sheet fromadverse effects of the heat thereon.

There has in recent years been proposed an radiation image recording andreproducing system in which a radiation image of an object can beproduced by using a stimulable phosphor. The stimulable phosphor, whenexposed to a radiation such as X-rays, α-rays, β-rays, γ-rays, cathoderays, or ultraviolet rays, stores a part of the energy of the radiation.When the stimulable phosphor exposed to the radiation is exposed tostimulating rays such as visible light, the stimulable phosphor emitslight in proportion to the stored energy of the radiation. The radiationimage recording and reporducing system employs such a stimulablephosphor. More specifically, the radiation image of an object such as ahuman body is stored in a sheet having a stimulable phosphor(hereinafter referred to as a "stimulable phosphor sheet" or a "phosphorsheet"), and then the stimulable phosphor sheet is scanned withstimulating rays such as a laser beam to cause the stimulable phosphorsheet to emit light representative of the radiation image. The emittedlight is photoelectrically detected and converted to an electric imagesignal which is processed to reproduce a visible image on a recordingmedium such as a photographic light-sensitive material or on a displayunit such as a cathode ray tube (CRT). The aforesaid radiation imagerecording and reproducing system is disclosed in Japanese Laid-Openpatent publication No. 55-12429 or 56-11395, for example.

The radiation image recording and reproducing system of the typedescribed above is of greater practical advantage than conventionalradiographic systems using a combination of an intensifying screen andan X-ray film in that images can be recorded in a wide range ofradiation exposure. More specifically, it is known that the amount oflight emitted from a stimulable phosphor upon stimulation thereof isproportional in a highly wide range to the amount of radiation to whichthe stimulable phosphor has been exposed. Therefore, even if the amountof radiation to which the stimulable phosphor is exposed varies widelyunder various conditions, radiation images free from such exposurevariations can be obtained by selecting a suitable read-out gain in thephotoelectric transducer for reading and converting the emitted lightinto an electric signal, and processing the electric signal into avisible image on a recording medium such as photographic light-sensitivematerial or on a display unit such as a CRT.

The radiation image recording and reproducing system is capable ofprocessing a converted electric signal to produce a visible image on arecording medium or a display unit so that the radiation image can wellbe observed for diagnostic purpose. In this system, the stimulablephosphor sheet does not serve as a final image recording medium, but asa temporary image storage medium for eventually transferring images tothe final recording medium or display unit. Therefore, the stimulablephosphor sheet can be used repeatedly, and is economical and convenientif in repetitive use.

To reuse the stimulable phosphor sheet, the residual radiation energy onthe stimulable phosphor sheet after the radiation image has been readout by stimulating rays is discharged by exposure to light having awavelength within the stimulating wavelength for the stimulable phosphorconstituting the stimulable phosphor sheet. The erasure of theirradiation energy from the stimulable phosphor sheet is disclosed inJapanese Laid-Open patent publication No. 56-11392 or 56-12599, forexample.

More specifically, it is necessary to discharge all of the radiationenergy remaining on the stimulable phosphor sheet in order to erase anyresidual irradiation image. Therefore, the residual image should becompletely erased by being exposed to as much intensive light emittedfrom an erasure light source as possible because if any radiation imageremained on the phosphor sheet, it would adversely affect a nextradiation image of the object to be stored on the phosphor sheet, and noaccurate image would be available of the object.

In order to erase the residual image completely and in short time fromthe phosphor sheet with the erasure light, an increased number oferasure light sources and an increased amount of erasure light should beemployed to generate intensive erasure light. The increased number oferasure light sources and the increased amount of erasure light howevertend to heat the image erasure unit excessively. The image erasure unit,the stimulable phosphor sheet, and surrounding components are thereforeliable to be damaged by the heat of the erasure light emitted. Inaddition, the generation of the intensive erasure light requires alarge-size power supply which makes the entire system large in size andwhich also makes it difficult to maintain and service the system.

If the image erasure unit is to be more compact and installed in asmaller space, the number of light sources for emitting erasure lightwill be restricted and the amount of erasure light emitted will bereduced. Therefore, the stimulable phosphor sheet carrying a residualimage to be erased should remain placed in the image erasure unit for anincreased period of time. As a result, the cyclic period in which to usethe stimulable phosphor sheet for the storage of a radiation image willbe increased.

SUMMARY OF THE INVENTION

It is a primary object of the present invention to provide a radiationimage erase unit for erasing a residual radiation image from astimulable phosphor sheet by exposing the same to erasure light in aradiation image recording and read-out system having an image read-outunit for irradiating stimulable phosphor sheet with stimulating rays tocause the same to emit light representative of the radiation imagestored therein, for detecting the light emitted from the stimulablephosphor sheet, and for converting said emitted light photoelectricallyto an electric signal, the radiation image erase unit comprising: acasing; erasure light source means disposed in the casing for emittingthe erasure light; feeder means for delivering the stimulable phosphorsheet for the casing; and heat radiator means mounted on the casing forforcibly radiating heat out of the casing.

Another object of the present invention is to provide a radiation imageerase unit for erasing a residual radiation image from a stimulablephosphor sheet by exposing the same to erasure light in an irradiationimage recording and read-out system having an image read-out unit forirradiating the stimulable phosphor sheet with stimulating rays to causethe same to emit light representative of the irradiation image storedtherein, for detecting the light emitted from the stimulable phosphorsheet, and for converting said emitted light photoelectrically to anelectric signal, the radiation image erase unit comprising: theradiation image erase unit comprising: a casing; erasure light sourcemeans disposed in the casing for emitting the erasure light; and feedermeans for delivering the stimulable phosphor sheet for the casing, thecasing having inner panel surfaces for reflecting the light emitted fromthe erasure light source means.

Still another object of the present invention is to provide a radiationimage erase unit for erasing a residual radiation image from astimulable phosphor sheet by exposing the same to erasure light in aradiation image recording and read-out system having an image read-outunit for irradiating the stimulable phosphor sheet with stimulating raysto cause the same to emit light representative of the radiation imagestored therein, for detecting the light emitted from the stimulablephosphor sheet, and for converting said emitted light photoelectricallyto an electric signal, the radiation image erase unit comprising: acasing; erasure light source means disposed in the casing for emittingthe erasure light; and feeder means for delivering the stimulablephosphor sheet for the casing, the casing having a heat radiatingopening defined in at least one panel thereof, and a reflecting platedisposed between the panel and the erasure light source means inconfronting relation to the opening.

The above and other objects, features and advantages of the presentinvention will become more apparent from the following description whentaken in conjunction with the accompanying drawings in which preferredembodiments of the present invention are shown by way of illustrativeexample.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a radiation image recording and read-outsystem;

FIG. 2 is a vertical cross-sectional view of the radiation imagerecording and read-out system shown in FIG. 1;

FIG. 3 is an enlarged vertical cross-sectional view of a radiation imageerase unit for a stimulable phosphor sheet according to the presentinvention;

FIG. 4 is a perspective view, partly cut away, of the radiation imageerase unit;

FIG. 5 is a side elevational view of the radiation image erase unitshown in FIG. 3;

FIG. 6 is a perspective view of the radiation image erase unit shown inFIG. 3;

FIG. 7 is a fragmentary view showing the relationship between a mirroredlayer or diffusion layer on the inner surface of a casing side wall, alight source, and reflected light; and

FIG. 8 is a cross-sectional view of a radiation image erase unitaccording to another embodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

A radiation image recording and read-out system incorporating therein animage recording unit, an image read-out unit, and an image erase unit ofthe invention will first be described with reference to FIGS. 1 and 2.

The reference numeral 10 in FIG. 1 denotes an upstanding radiation imagerecording and read-out system including a first vertical housing 12 anda second horizontal housing 14. The first housing 12 supports anexposure unit or image recording unit 16 on a front upper portionthereof and a control unit 18 on a side upper wall thereof.

The arrangements in the first and second housings 12, 14 will bedescribed with reference to FIG. 2. A pair of sheet reception rollers 20for receiving a stimulable phosphor sheet on which an image is recordedis disposed in a lower portion of the image recording unit 16. Below theroller pair 20, there are disposed a first pair of confronting guidemembers 22 and a second pair of confronting guide members 24, each pairextending in the vertical direction. There is a roller pair disposedbetween the first and second pairs of guide members 22, 24,respectively. A pair of third confronting guide members 26 is locatedbeneath the first and second pairs of guide members 22, 24 with anotherroller pair disposed therebetween. Roller pairs are rotatably disposedbetween the third pair of guide members 26 and a fourth guide member 28disposed therebelow.

A first endless feed belt 30 is disposed partly against the fourth guidemember 28 and has an angularly bent configuration at an inner corner ofthe first housing 12. The first feed belt 30 terminates at a lowercentral portion of the second housing 14. A second endless feed belt 32is disposed in a slightly spaced relation to the terminal end of thefirst endless feed belt 30. The second endless feed belt 32 is angularlybent in an upward direction at an inner corner of the second housing 14.A group of four rollers 34 is held against the inner bent portion of thesecond feed belt 32. Third and fourth successively positioned endlessfeed belts 36, 38 respectively, extend horizontally with the third belt36 in slightly spaced relation to the terminal end of the feed belt 32.A fifth endless belt 40 bent upwardly is located in the vicinity of theterminal end of the fourth feed belt 38. A group of three rollers 42 isheld against a surface of the belt 40.

The fifth belt 40 and the roller group 42 are located beneath a pair ofconfronting guide members 44 disposed below a pair of confronting guidemembers 46 with a pair of confronting rollers interposed therebetween.Above the guide members 46, there is positioned radiation image eraseunit 100 of the present invention which will be described in detaillater on. Relatively short guide members 48 are disposed above theradiation image erase unit 100, and other guide members 50 are locatedabove the guide members 48. An endless feed belt 52 of a bentconfiguration is disposed in the vicinity of the terminal ends of theguide members 50 in a substantially top portion of the first housing 12.A roller group 54 is held against a curved inner run of the feed belt52. Below the feed belt 52 and the roller group 54, there are disposedtwo pairs of rollers 56, 58 for supplying a stimulable phosphor sheetinto the image recording unit 16.

The feed system for a stimulable phosphor sheet has the above basicconstruction in the radiation image recording and read-out system 10.

The image read-out unit, designated at 62, positioned in relation to thefeed system will be described.

The image read-out unit 62 is basically composed of a laser beam source64, a scanning optical system 63 including a galvanometer mirror forscanning a laser beam emitted from the laser beam source 64 over astimulable phosphor sheet, a reflecting mirror 66 for collecting light,and a light collecting optical element 68 for effectively collectingpart of light emitted from the stimulable phosphor sheet by the scanninglaser beam, and also light reflected by the reflecting mirror 66. Aphotomultiplier (photoelectric conversion device) 70 is mounted on thetop of the light collecting optical element 68.

The radiation image erase unit 100 according to the present invention isshown in detail in FIG. 3. The radiation image erase unit 100essentially comprises a casing 102, a pair of feeders 104, 106 mountedon the lower and upper ends, respectively, of the casing 102, and firstthrough fourth light sources 108a through 108d (FIG. 5) for emittingerasure light into the casing 102. The light sources 108a, 108d aremounted on a side panel 102a of the casing 102 and widely spaced fromeach other in parallel relation, while the light sources 108b, 108c aremounted on an opposite side panel 102b of the casing 102 and closelyspaced from each other in parallel relation. Thus, the light sources108b, 108c are located vertically between the light sources 108a, 108d.The side panel 102a has a large service opening which is closed by anopenable cover 109 fastened as by screws to the side panel 102a. Anangle member 110 is fixed to the lower end of the casting 102. Thecasing 102 can be fixed to the first housing 12 by attaching the anglemember 110 to the first housing 12.

The casing 102 has inlet and outlet slots 112a, 112b defined in upperand lower panels thereof adjacent to the feeders 104, 106, respectively.Guide members 114a, 114b are disposed in parallel relation in the casing102 and extend from the inlet slot 112a to the outlet slot 112b as shownin FIG. 5. The feeder 104 is composed of a pair of nip rollers 116a,116b held in rolling contact with each other and enclosed in a firstcover 117a attached to the lower panel of the casing 102. Likewise, thefeeder 106 is composed of a pair of nip rollers 118a, 118b held inrolling contact with each other and enclosed in a second cover 117battached to the upper panel of the casing 102. Resilient members 120a,120b such as coil springs are engaged by pins attached to the covers117a, 117b, respectively, and held in engagement with the rotatableshafts of the nip rollers 116b, 118b for normally urging them to beforcibly pressed against the nip rollers 116a, 118a, respectively. Thecovers 117a, 117b have slots 122a, 122b, respectively, aligned with theinlet and outlet slots 112a, 112b, respectively.

As shown in FIG. 3, a microswitch 126 is mounted on the casing 102 tofunction as a limit switch and has a detecting arm 128 held in slidingcontact with the nip roller 116b. A motor 130 is fixed to the casing 102closely to the angle 110 and has a rotatable shaft 132 to which a firstsprocket 134 is fixed. A chain 136 is trained around the first sprocket134, a second sprocket 138 fixed coaxially to the nip roller 116a, and athird sprocket 140 fixed coaxially to the nip roller 118a. The chain 136is also trained around a fourth tensioning sprocket 142 rotatablymounted on the side panel 102a of the casing 102. The fourth sprocket142 is supported on a shaft 144 displaceable in a slot 148 defined in aholder 146 attached to the side panel 102a for giving the chain 136 anoptimum tension.

The radiation image erase unit 100 includes a heat radiator for forciblycooling the casing 102. As shown in FIGS. 3, 5, 6 and 8, the heatradiator is composed of a relatively small opening 154 defined in thecover 109 fastened to the casing 102, a plurality of openings 158athrough 158d (four openings in the illustrated embodiment) defined in aside panel 156 of the casing 102 and each larger than the opening 154,and a plurality of motor-driven fans 160a through 160d (fourmotor-driven fans in the illustrated embodiment) disposed respectivelyin the openings 158a through 158d and drivable in synchronism withenergization of the sources 108a through 108d. A duct 162 of arectangular cross section is mounted on the side panel 156 insurrounding relation to the openings 158a through 158d and hence themotor-driven fans 160a through 160d. The duct 162 has an opening 164 atits distal end extending through the first housing 12, the opening 164communicating with the exterior of the radiation image recording andread-out system 10 (FIG. 2). The motor-driven fans 160a through 160d maybe mounted on the distal end of the duct 162 disposed out of the system10, rather than on the side panel 156 over the openings 158a through158d. The number of motor-driven fans employed may appropriately beselected dependent on the r.p.m. thereof and in view of otherconsiderations.

The side panels 102a through 102d and the side panel 156 of the casing102 have inner surfaces of a mirror finish. Where the casing 102 isconstructed of a metal sheet, it is preferable to grind the innersurfaces of the casing 102 to a mirror finish. However, the casing 102may be made of any suitable material, and the inner surfaces of the sidepanels 102a through 102d and the side panel 156 may be coated with thinfilms 111 of a mirror finish, as illustrated in FIG. 3.

A reflecting plate 166 smaller in area than the side panel 156 isdisposed in the casing 102 and mounted on the side panel 156 by bolts168 threaded at both ends thereof or other fasteners, the reflectingplate 166 being spaced from the inner surface of the side panel 156. Thereflecting plate 166 is positioned as closely to the light sources 108athrough 108d as possible, and has a surface 170 of a mirror finish whichfaces the light surfaces 108a through 108d. Alternatively, the surfaceof the reflecting plate 166 facing the light sources 108a through 108dmay be coated with a thin reflecting film or provided with a thinreflecting sheet.

The inner wall surfaces 111 of the casing 102 and the reflecting surface170 of the reflecting plate 166 may also be capable of diffusing lightfalling thereon. Such a diffusive reflecting surface 113 may be disposedsubstantially fully over the side panel of the casing 102 which facesthe stimulable phosphor sheet in the casing 102. It is preferablehowever that all of the substantially entire inner surfaces of the sidepanels of the casing 102 comprise such diffusive reflecting surfaces 113as shown in FIG. 4.

The diffusive reflecting surfaces 113 may be produced in the casing 102in various ways. For example, the inner panel surfaces of the casing 102may be coated with a paint containing a white pigment. As analternative, panels containing a white pigment may be applied to theinner panel surfaces of the casing 102. Where the inner panel surfacesof the casing 102 are coated with a paint containing a white pigment, itis preferable to coat the paint in a baking finish process. The panelcontaining a white pigment may comprise a panel with a white pigmentpaste mixed therein, or a panel composed of a support painted with awhite pigment.

The white pigment may be in the form of inorganic white powder ororganic white powder. However, the inorganic white powder is preferredfor its better heat resistance.

Examples of the inorganic white powder include titanium dioxide,magnesium oxide, basic lead carbonate (2PbCO₃·Pb(OH)₂), barium sulfate,aluminum oxide, alkaline earth metal halide (for example, barium fluorohalide such as BaFCl, BaFBr), calcium carbonate, zinc oxide, antimonyoxide, silicon dioxide, lithopone, magnesium silicate, basic silicatewhite lead, basic phosphate white lead, and aluminum silicate.

Operation of the radiation image erase unit thus constructed will bedescribed below.

An object (not shown) held against an exposure surface 60 of the imagerecording unit 16 is exposed to a radiation, and a radiation image ofthe object is recorded on a stimulable phosphor sheet S. The stimulablephosphor sheet S is then fed through the rollers 20, the guide members22, 24, 26, 28, and the endless belts 30, 32, 36 to the image read-outunit 62. In the image read-out unit 62, the stimulable phosphor sheet Sis scanned through the scanning optical system 63 by a laser beamemitted from the laser source 64 to emit light which is reflecteddirectly or by the mirror 66 to the optical device 68. The light fromthe optical device 68 is then converted by the photomultiplier 70 to anelectric signal that is fed to an image reproducing unit (not shown).

After the radiation image has been read from the stimulable phosphorsheet S, the stimulable phosphor sheet S is fed by the feed belts 38, 40through the guide members 44 and the guide members 46 to the nip rollers116a, 116b. The stimulable phosphor sheet S as introduced into the inletslot 122a is led by the nip rollers 116a, 116b to the guide members114a, 114b. When the stimulable phosphor sheet S is pinched between thenip rollers 116a, 116b, the nip roller 116b is displaced by the sheet Saway from the nip roller 116a against the tension of the coil spring120a to push the detecting arm 128 of the microswitch 126. Themicroswitch 126 then generates a signal to energize the motor 130,whereupon the chain 136 is moved to rotate the second sprocket 138.Since the second sprocket 138 is fixed coaxially to the nip roller 116a,the nip roller 116a is rotated to deliver the stimulable phosphor sheetS toward the guide members 114a, 114b while the nip roller 116b is alsobeing rotated.

As described above, the microswitch 126 is turned on to energize themotor 130 when the stimulable phosphor sheet S reaches the nip roller116b and displaces the same. Upon rotation of the motor 130, the thirdspocket 140 also rotates the nip rollers 118a, 118b. As the leading endof the stimulable phosphor sheet S moves through the guide members 114a,114b and reaches the nip rollers 118a, 118b, the trailing end of thestimulable phosphor sheet S leaves the nip rollers 116a, 116b. The niproller 116b is now displaced in the direction of the arrow A (FIG. 3)toward the nip roller 116a under the resiliency of the coil spring 120a.As a result, the detecting arm 128 of the microswitch 126 is alsodisplaced in the direction of the arrow A, and the microswitch 126issues a signal to reverse the motor 130. The stimulable phosphor sheetS with its leading end gripped by the nip rollers 118a, 118b is thenmoved back toward the nip rollers 116a, 116b. When the trailing end ofthe sheet S is gripped again between the nip rollers 116a, 116b, the niproller 116b and hence the detecting arm 128 are displaced again toenable the microswitch 126 to issue a signal for de-energizing the motor130. Now, the stimulable phosphor sheet S is held between the niprollers 116a, 116b and the nip rollers 118a, 118b.

The light sources 108a, 108b, 108c, and 108d are energized to emit lightwhich is reflected sufficiently back and forth in the casing 102 toerase any residual radiation image from the stimulable phosphor sheet S.More specifically, since the light sources 108a through 108d aredisposed parallel to each other, light emitted from the light sources108a through 108d directly illuminate the surface of the stimulablephosphor sheet S uniformly. Part of the emitted light is reflected bythe mirror-finish surfaces 111, 170 or the diffusive reflecting surfaces113 to fall on the sheet S (see FIG. 7). The residual radiation imagecan therefore completely be erased from the stimulable phosphor sheet S.The erasure light emitted from the light sources 108a through 108d has awavelength in the range of stimulating wavelengths of the stimulablephosphor sheet S.

In synchronism with the energization of the light sources 108a through108d, the motor-driven fans 160a through 160d are actuated to cause hotair heated by the light sources 108a through 108d in the casing 102 toflow in the direction of the arrow B (FIG. 3) into the duct 162 fromwhich the hot air is discharged out of the erase unit 100. At the sametime, cool air is introduced by the motor-driven fans 160a through 160dthrough the opening 154 into the casing 102 which is forcibly cooled bythe introduced cool air.

Since the side panel 156 has the holes 158a through 158d for heatradiation, the inner reflecting surface on the side panel 156 has areduced area which has a low light reflecting capability which wouldimpair the intended function of the erase unit 100. However, thereflecting plate 166 with its inner surface having a mirror finish ordiffusive reflecting layer is mounted on the side panel 156 parallelthereto. Therefore, the reflecting surface of a sufficient area isdisposed over the holes 158a through 158d to provide a required lightreflecting ability. Inasmuch as the reflecting plate 166 is positionedclosely to the light sources 108a through 108d, it can reflect intensiveerasure light toward the stimulable phosphor sheet S.

A prescribed period of time after the light sources 108a through 108dhave been energized, the motor 130 is energized again to move the chain136 to cause the nip rollers 118a, 118b to feed the stimulable phosphorsheet S toward the guide members 48. Since the residual image iscompletely erased from the stimulable phosphor sheet S upon arrival atthe guide members 48, a next radiation image can well be recorded on andstored in the stimulable phosphor sheet S which has been delivered intothe image recording unit 16 through the endless belt 52 and the rollers52, 58.

FIG. 8 shows a radiation image erase unit according to anotherembodiment of the present invention. The radiation image unit of FIG. 8is separated physically from the image recording unit and the imageread-out unit, and is preferably installed independently of such otherunits. Identical or corresponding parts shown in FIG. 8 are denoted byidentical or corresponding reference characters employed in the previousembodiment.

As shown in FIG. 8, the radiation image unit, designated at 100,includes a casing 102 having an opening 172 defined in a side panelthereof, the opening 172 being large enough to allow an image storageportion of a stimulable phosphor sheet S to be sufficiently exposed toerasure light from the light sources 108a through 108d. A feed belt 174is disposed outside of the casing 100 proximate to the opening 172. Thefeed belt 174 is driven by a roller 176, and a roller 178 is pressedagainst the belt 174 in alignment with the roller 176. The casing 100has inner panel surfaces which are of a mirror finish or coated with athin film or sheet of a mirror finish, or which comprise diffusivesurfaces. A reflecting plate 166 is mounted in the casing 100 andsupported by bolts 168 on a side panel 156 in parallel spaced relationthereto for optically shielding holes 158a through 158d from the erasurelight sources 108a through 108d.

When the stimulable phosphor sheet S is fed along in the direction ofthe arrow C, it is sandwiched between the roller 178 and the feed belt174 and delivered toward the opening 172. When the sheet S is positionedbeneath the opening 172, it is exposed to erasure light emitted from theerasure light sources 108a through 108d to erase any residual image fromthe sheet S. More specifically, the erasure light from the erasure lightsources 108a through 108d falls on the sheet S, directly or throughreflection by the mirrored inner panel surfaces of the casing 102 andthe mirrored or diffusive surface of the reflecting plate 166. After theresidual image has been erased, the feed belt 174 is driven again tofeed the sheet S in the direction of the arrow D. With the arrangementof FIG. 8, the radiation image erase unit 100 is not completely shieldedagainst leakage of light therefrom because of the opening 172 whichallows the light to leak out. However, since the radiation image eraseunit of FIG. 8 is installed independently of and away from the imagerecording and read-out units, no problem occurs from such aconstruction. Rather, the radiation image erase unit of FIG. 8 isadvantageous in that it can be manufactured inexpensively. The radiationimage erase unit can be disposed proximate to the image recording andread-out units if a suitable light shielding member is combined with theradiation image erase unit.

With the arrangement of the present invention, as described above, aradiation image erase unit for use with a stimulable phosphor sheet iscomposed of a casing, feeder means mounted on the casing for feeding astimulable phosphor sheet, erasure light sources disposed in the casingfor emitting light, and a heat radiator on the casing for radiating theheat of the light sources from the casing. The stimulable phosphor sheetand surrounding components are therefore protected from damage due tothe heat which would otherwise be trapped in the casing. Since theradiation image unit is in the form of the casing, it can simply beincorporated into a radiation image recording and read-out system, andonly takes up a small space so that the system itself can be madecompact in size.

The inner panel surfaces of the casing are of a mirror finish or coatedwith a thin film or sheet of a mirror finish or diffusive nature. Thelight emitted from the erasure light sources is, directly or throughreflection from the inner panel surfaces, directed to the stimulablephosphor sheet to erase any residual radiation image completely from thesheet. Since no residual radiation image remains on the sheet, a nextradiation image can well be recorded and stored in the sheet.

The erase unit also includes a reflecting plate disposed in the casingadjacent to the erasure light sources. The light emitted from theerasure light sources falls, directly or via reflection from thereflecting plate, on the stimulable phosphor sheet for complete erasureof any residual radiation image from the stimulable sheet. The casinghas heat radiator holes for radiating heat from the casing, and thereflecting plate is disposed closely to the holes for a light reflectingcapability over the holes.

The present invention may be incorporated in a bed-type radiation imagerecording and read-out system, a radiation image read-out system havingan image read-out unit and an image erase unit and separated from animage recording unit, or a radiation image erase unit independent of animage read-out unit and an image recording unit for the sole purpose oferasing residual radiation images.

Although certain preferred embodiments have been shown and described, itshould be understood that many changes and modifications may be madetherein without departing from the scope of the appended claims.

What is claimed is:
 1. A radiation image erase unit for erasing aresidual radiation image from a stimulable phosphor sheet by exposingthe sheet to erasure light in a radiation image recording and read-outsystem having an image read-out system having an image read-out unit forirradiating said stimulable phosphor sheet with stimulating rays tocause the sheet to emit light representative of said radiation imagestored therein, for detecting said light emitted from said stimulablephosphor sheet, and for converting said emitted light photoelectricallyinto an electric signal, said radiation image erase unit comprising: acasing; erasure light source means disposed in said casing for emittingthe erasure light; and feeder means for delivering said stimulablephosphor sheet into said casing, said casing having a heat radiatingopening defined in at least one panel thereof, and a reflecting plate(166), disposed between said panel and said erasure light source meansin confronting relation to said opening, for reflecting the erasurelight from said light source means toward said sheet.
 2. A radiationimage erase unit according to claim 1, wherein said reflecting plate hasa surface of a mirror finish facing said erasure light source means. 3.A radiation image erase unit according to claim 1, wherein saidreflecting plate has a thin reflecting film or sheet attached to asurface thereof facing said erasure light source means.
 4. A radiationimage erase unit according to claim 1, wherein said casing has an innerpanel surface which is at least partially of a mirror finish.
 5. Aradiation image erase unit according to claim 1, wherein said casing hasa thin reflecting film or sheet attached to at least a portion of aninner panel surface thereof.
 6. A radiation image erase unit accordingto claim 1, including a plurality of heat radiating openings defined insaid one panel.
 7. A radiation image erase unit according to claim 1,including a motor-driven fan disposed over said heat radiating opening.8. A radiation image erase unit according to claim 1, including a ductmounted on said casing in communication with said heat radiating openingfor discharging heated air out of said casing through said opening andsaid duct.